Suspected distortion of citations in high-impact cancer journals

Research and scholarship are shaped by article citations, which underpin the communication of ideas, assignment of credit, journal impact factors, and author career progression. Given their key influence on author and journal metrics, citations can be intentionally manipulated to inflate the reputation of journals and researchers. Paper mills, unethical organisations that produce and sell manuscripts and publishing services, may also be manipulating citations, but the extent of this manipulation is unknown. Here, we show that molecular cancer articles sharing features with retracted papers from paper mills display citation patterns that suggest systematic inflation. These articles were published in journals in the top decile of journal rankings. Suspected paper mill articles received 50 to 100% more citations than other papers 1 to 3 years after publication, while paradoxically attracting fewer readers and online accesses. Suspected paper mill articles also cited - and were cited by - other suspected paper mill articles and appeared in journals previously reported as paper mill targets. The resulting citations from suspected paper mill articles measurably inflated journal citation metrics. These findings suggest that paper mills inflate the citation metrics of supported publications and affected journals. The manipulation of citation metrics at scale may amplify unreliable findings, slowing scientific progress, and providing unreasonable citation benchmarks for research articles, journals and authors. Our findings highlight new risks in relying on citation metrics for research and journal evaluation and support the use of more robust metrics to describe article and journal quality.